DM74LS240N

Overview

The DM74LS240N is an octal 3-STATE buffer and line driver manufactured by onsemi (originally Fairchild Semiconductor). It features inverted outputs, operates within a supply voltage range of 4.75V to 5.25V, and utilizes a 20-Lead Plastic Dual-In-Line Package (PDIP) with a 0.300-inch width. The device provides typical sink current of 24 mA and source current of -15 mA. Propagation delays are typically 10.5 ns for inverting paths, with enable/disable times around 18 ns.

Feature Summary

• Features PNP data inputs that reduce DC loading on bus lines while providing improved noise rejection through hysteresis.
• Provides 3-STATE outputs capable of driving bus lines directly or terminated loads down to 133Ω.

Applications

• Memory-address drivers
• Clock drivers
• Bus-oriented transmitters and receivers

Procurement Notes

Verify the manufacturer origin, as this component was originally produced by Fairchild Semiconductor before its acquisition by onsemi. Confirm the package type matches the specific ordering code suffix required for your assembly process. Ensure the design accounts for the recommended operating temperature range of 0°C to +70°C.

Selection Notes

Select this component when inverted logic buffering is required for high fanout applications. The LS series offers standard TTL compatibility with moderate speed performance. Consider the non-inverting DM74LS241 if signal phase preservation is necessary instead of inversion.

Part Context

This part belongs to the 74LS family of logic integrated circuits, designed for general-purpose digital applications. It serves as a buffer and line driver variant within the broader octal 3-STATE logic family, sharing pinouts and electrical characteristics with related devices like the DM74LS241.

Replacement Considerations

Direct functional equivalents include the SN74LS240 from Texas Instruments. Verify pin compatibility and electrical specifications against the original datasheet requirements before substitution.

FAQ

What is the purpose of the hysteresis at the data inputs?

The 400 mV hysteresis at each low current PNP data input improves noise margins and enhances noise rejection capabilities.

Can this device drive terminated transmission lines?

Yes, the device is designed to drive terminated lines down to 133Ω impedance.